Noise from TB6600 motor controller

Other Hardware Motors, Mechanics, Power and CNC
1

Dear All,

I have a very annoying problem. I made a circuit of several subcomponents.

I have an Arduino UNO, which is the main board in my setup. It has an Arduino NANO connected to it (A4,A5, +5V and GND), and there is a 2-channel level shifter with a small DC-DC converter to convert the +5V of the UNO to +1.6V. The level shifter is used to shift the logical level of a digital caliper so I can read it with the UNO. Then, the NANO has a TB6600 connected to it (D8, D9, +5V), so I control the stepper motor with a separate board which receives the commands from the UNO. Also, there is a HX711 connected to the UNO for reading a load cell. Interestingly, this board is not affected by the noise, however it also uses the shared +5V and GND rails.

When I connect the USB to the main board, everything works nicely, the digital caliper gives signal, I can read the position with it...etc. However, when I connect the TB6600 to a power supply (I tried 4 different types), the readings of the digital caliper go crazy. I checked the signal of the digital caliper with an oscilloscope and I could see that the square waves change when I connect the PSU to the TB6600. It is like some extra edges are added to the square waves. I guess, that's the noise. So all of a sudden, the reading becomes 400 mm instead of 1.2 mm or something like that.

I removed the three pins of the TB6600 from the NANO, but I kept it powered. The caliper was still showing crazy numbers. Is it possible that the caliper picks up some sort of radio noise? How can I troubleshoot this issue? I tried different stepper motor controller, but I experienced the same issue.

Thank you for your ideas and help!

2

Stepper drivers kick out loads of noise if you let them.

Keep all motor wiring in twisted pairs, one pair per winding, screened if possible too. All motor wiring and power wiring to the TB6600 should be well away from any sensor wires - although the better everything is shielded the less issue there will be.

You may have a ground loop if the caliper is grounded to the machinery, and the motors are too, transmitting switching noise. Some insulating barrier might be effective here if that's an issue (easy to test for, remove the caliper from the machinery).

Cheap supplies can transmit noise between mains and their outputs, in either direction. Worth checking the Arduino 5V rail for noise with the 'scope.